U.S. patent number 6,135,920 [Application Number 09/335,739] was granted by the patent office on 2000-10-24 for apparatus and method for automatically starting and stopping a vehicle engine to effect a smooth change from a vehicle brake release state to a vehicle drive state.
This patent grant is currently assigned to Denso Corporation. Invention is credited to Masaru Kamiya, Akira Kato, Takahiro Souki.
United States Patent |
6,135,920 |
Kamiya , et al. |
October 24, 2000 |
Apparatus and method for automatically starting and stopping a
vehicle engine to effect a smooth change from a vehicle brake
release state to a vehicle drive state
Abstract
An engine automatic speed control apparatus which exhibits a
smooth transition from brake release to an engine drive state. An
ECU determines braking force such that a vehicle does not move in
correspondence with the slope of a road surface according to a road
surface slope sensor while monitoring an operated quantity of a
brake pedal according to a brake pedal operated-quantity sensor.
The ECU stops an engine when braking force is applied via the brake
pedal such that the vehicle does not move. After stopping the
engine, the ECU determines braking force such that the vehicle does
not move in correspondence with slope of the road surface according
to the road surface slope sensor, and restarts the engine when
braking force becomes less than braking force required to maintain
the vehicle in a stopped state. The ECU then restarts the engine in
the interval from relaxing of braking force via the brake pedal
until the brake pedal is released.
Inventors: |
Kamiya; Masaru (Toyoake,
JP), Kato; Akira (Anjo, JP), Souki;
Takahiro (Toyota, JP) |
Assignee: |
Denso Corporation (Kariya,
JP)
|
Family
ID: |
15960026 |
Appl.
No.: |
09/335,739 |
Filed: |
June 18, 1999 |
Foreign Application Priority Data
|
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Jun 19, 1998 [JP] |
|
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10-173415 |
|
Current U.S.
Class: |
477/185; 477/203;
477/204 |
Current CPC
Class: |
B60W
10/04 (20130101); B60W 10/06 (20130101); B60W
30/1819 (20130101); F02D 41/408 (20130101); F02N
11/0818 (20130101); B60W 10/18 (20130101); B60W
30/18027 (20130101); F02D 11/105 (20130101); B60W
30/18118 (20130101); Y02T 10/40 (20130101); B60W
2540/12 (20130101); F02N 2200/102 (20130101); F02N
2200/124 (20130101) |
Current International
Class: |
F02D
41/40 (20060101); F02D 11/10 (20060101); B60K
041/20 () |
Field of
Search: |
;477/185,189,201,203,204,4,21,27 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
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|
|
57-183538 |
|
Nov 1982 |
|
JP |
|
58-38346 |
|
Mar 1983 |
|
JP |
|
59-110346 |
|
Jul 1984 |
|
JP |
|
9-209790 |
|
Aug 1997 |
|
JP |
|
Primary Examiner: Estremsky; Sherry L.
Attorney, Agent or Firm: Pillsbury Madison & Sutro
LLP
Claims
What is claimed is:
1. A motor vehicle engine control apparatus, comprising:
a control device for controlling an engine to restart the engine
after engine stoppage accompanying operation of a braking force
operating member in an interval after alleviation of braking force
by said braking force operating member until said braking force
operating member is released.
2. The motor vehicle engine control apparatus of claim 1, wherein
said control device restarts said engine when said braking force
becomes smaller than a predetermined value.
3. The motor vehicle engine control apparatus of claim 1, further
comprising a hydraulic pressure sensor for detecting hydraulic
brake pressure in a vehicle hydraulic brake circuit, said control
device restarting said engine in response to received signals from
said hydraulic pressure sensor.
4. The motor vehicle engine control apparatus of claim 1, further
comprising a braking force operating member sensor for detecting
operation of said braking force operating member, said control
device restarting said engine in response to received signals from
said braking force operating member sensor.
5. The motor vehicle engine control apparatus of claim 4, wherein
said braking force operating member is a switch to output a
switching signal at a predetermined operating position.
6. The motor vehicle engine control apparatus of claim 4, wherein
release of said braking force operating member is detected via
detection of an operating direction of said braking force operating
member by an operating direction sensor.
7. The motor vehicle engine control apparatus of claim 1, wherein
said control device stops said engine when braking force becomes
larger than a first predetermined value, and restarts said engine
when braking force becomes smaller than a second predetermined
value.
8. The motor vehicle engine control apparatus of claim 7, wherein
said first predetermined value equals said second predetermined
value.
9. The motor vehicle engine control apparatus of claim 1, wherein
said engine control device stops said engine when a braking force
sufficient to keep said vehicle stationary is applied, and restarts
said engine when said braking force becomes less than sufficient to
keep said vehicle stationary.
10. The motor vehicle engine control apparatus of claim 9, further
comprising a slope sensor for determining road surface slope,
wherein said engine control device causes a sufficient braking
force to be generated such that said vehicle does not move in
accordance with said road surface slope according to said slope
sensor.
11. The motor vehicle engine control apparatus of claim 1, further
comprising a braking force control device for applying a
predetermined braking force such that said vehicle does not move at
least while said engine is stopped.
12. The motor vehicle engine control apparatus of claim 11, wherein
said braking force control device causes release of said
predetermined braking force when speed of said engine is greater
than or equal to a predetermined value.
13. The motor vehicle engine control apparatus of claim 11, wherein
said braking force control device causes release of said
predetermined braking force when speed of said engine is greater
than or equal to a predetermined value and an accelerator pedal is
depressed.
14. The motor vehicle engine control apparatus of claim 11, wherein
said braking force control device prohibits application of braking
force when a road surface slope according to a slope sensor is less
than or equal to a predetermined value.
15. The motor vehicle engine control apparatus of claim 11, wherein
said braking force control device causes release of said
predetermined braking force when engine speed reaches a fixed speed
range after engine starting.
16. The motor vehicle engine control apparatus of claim 11, wherein
said braking force control device prohibits application of braking
force when a braking force of another braking force operating
member is greater than or equal to a predetermined value.
17. The motor vehicle engine control apparatus of claim 11,
wherein:
each of a plurality of braking force operating members is provided
with means for maintaining braking force thereof; and
said braking force control device applies braking force when a sum
of respective braking forces of said plurality of braking force
operating members is less than or equal to a predetermined
value.
18. The motor vehicle engine control apparatus of claim 11, further
comprising a brake system hydraulic circuit for braking said
vehicle in response to said braking force being applied to said
braking force operating member, said brake system hydraulic circuit
including at least a master cylinder, a wheel cylinder and a
solenoid disposed between said master cylinder and said wheel
cylinder for controlling communication therebetween, wherein said
braking force control device applies a predetermined braking force
to maintain said vehicle in a stationary position by controlling
said solenoid.
19. The motor vehicle engine control apparatus of claim 12, wherein
said braking force control device restarts said engine when one of
a coil temperature of said solenoid reaches one of a predetermined
temperature and time since actuation of said solenoid reaches a
predetermined value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
The present application is related to, and claims priority from,
Japanese Patent Application No. Hei. 10-173415, the contents of
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to the control of motor
vehicle engine speed during a braking period, and more particularly
to automatic control of vehicle engine speed during a vehicle
braking period in which the vehicle is stopped, and subsequently
during the transition time from when the vehicle brake pedal is
released to when the vehicle again begins to move.
2. Description of Related Art
A conventional engine automatic speed control apparatus economizes
fuel and improves exhaust emissions when, for example, an
automobile stops at an intersection during city-street driving, by
automatically stopping, and thereafter restarting the engine under
predetermined conditions. Accordingly, the engine automatic speed
control apparatus described in Japanese Patent Application
Laid-open No. Hei 9-209790 restarts an engine from a stopped state
by causing release of a brake condition prior to operation of the
accelerator pedal.
However, in some cases, sufficient engine output is not obtained
when the accelerator pedal is operated after the brake is released.
Thus, it would be desirable to increase engine speed to a
sufficient output level before the accelerator pedal is depressed.
In particular, in a vehicle having an automatic transmission with a
torque converter, it may be difficult to perform travel known as
creeping, wherein the vehicle moves slowly when the shift lever is
in the "Drive" position even when the accelerator pedal is not
depressed.
SUMMARY OF THE INVENTION
In this regard, it is an object of the present invention to provide
an engine automatic speed control apparatus for a vehicle which can
smoothly change from a brake release state to an engine drive
state.
A vehicle engine automatic speed control apparatus according to the
present invention comprises a control unit for restarting an engine
after engine stoppage accompanying operation of a braking force
operating member. The control unit is for restarting the engine in
an interval from after braking force is alleviated by the braking
force operating member until the braking force operating member is
released.
As a result, the engine is started quickly, and sufficient engine
output is obtained when the accelerator is operated after releasing
the brake. In particular, in a vehicle provided with an automatic
transmission with a torque converter, travel via creeping after
brake release is possible.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overall structural view of an engine automatic speed
control apparatus according to a first embodiment of the present
invention;
FIG. 2 is an explanatory drawing indicating an operating range of
an accelerator pedal;
FIG. 3 is an explanatory drawing of a road surface slope
sensor;
FIG. 4 is a flow diagram for describing a mode of operation of the
first embodiment;
FIG. 5 is a flow diagram for describing a mode of operation of the
first embodiment;
FIG. 6 is a timing diagram for describing a mode of operation of
the first embodiment;
FIG. 7 is a map for determining required braking force;
FIG. 8 is a timing diagram for describing another example of the
first embodiment;
FIG. 9 is a timing diagram for describing another example of the
first embodiment;
FIG. 10 is a diagram of a brake hydraulic circuit according to a
second embodiment of the present invention;
FIG. 11 is a flow diagram for describing a mode of operation of the
second embodiment;
FIG. 12 is a timing diagram for describing a mode of operation of
the second embodiment;
FIG. 13 is a flow diagram for describing a mode of operation of a
third embodiment of the present invention;
FIG. 14 is a timing diagram for describing a mode of operation of
the third embodiment;
FIG. 15 is a flow diagram for describing a mode of operation of a
fourth embodiment of the present invention;
FIG. 16 is a flow diagram for describing a mode of operation of a
fifth embodiment of the present invention;
FIG. 17 is a timing diagram for describing a mode of operation of
the fifth embodiment;
FIG. 18 is a timing diagram for describing a mode of operation of a
sixth embodiment of the present invention;
FIG. 19 is a timing diagram for purpose of comparison;
FIG. 20 is a timing diagram for describing a mode of operation of a
seventh embodiment of the present invention;
FIG. 21 is a timing diagram for purpose of comparison;
FIG. 22 is a timing diagram for describing a mode of operation of
another example of the seventh embodiment; and
FIG. 23 is a timing diagram for describing a mode of operation of
an eighth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
First Embodiment
Embodiments of the present invention will be described hereinafter
with reference to the drawings.
The schematic structure of an engine in which the engine automatic
speed control apparatus of the present invention is applied, and
peripheral equipment thereof, will be described with reference to
FIG. 1. Specifically, an engine 1, which is preferably a four-cycle
gasoline engine is provided with injectors 2 and an igniter 3. An
electronic control unit (ECU) for engine-controlling use 4
calculates the fuel-injection quantity from signals such as
intake-air quantity, engine speed, and engine coolant-water
temperature to optimize the air-fuel ratio of the engine 1, and
causes an optimal fuel quantity to be injected from the injectors 2
disposed in the intake lines of the several cylinders. The ECU 4
controls the igniter 3 so that optimal ignition timing is obtained
from the signals indicating the engine speed and the load
state.
Meanwhile, an automatic transmission 5 is linked to the output
shaft of the engine 1. This automatic transmission 5 is made up of
a torque converter 6 to transmit the output of the engine 1, a
gearbox 7 driven by the torque converter 6, and a hydraulic circuit
(not illustrated) to switch the gear ratio of the gearbox 7 in
correspondence with vehicle-body speed and the output of the engine
1. The operating mode of the automatic transmission 5 is switched
via operation of a shift lever (not illustrated) disposed at the
driver's seat among the several ranges of "Park" (P), "Reverse"
(R), "Neutral" (N), "Drive" (D), "3rd Speed," "2nd Speed," and "1st
Speed." Accordingly, the hydraulic circuit in the automatic
transmission 5 is switched to obtain the optimal gear for the
selected operating state. The output of the automatic transmission
5 is transmitted to a differential gear 8, and a drive wheel 9 is
rotatably driven.
Additionally, an electronic control unit (ECU) 10 for automatically
starting and stopping the engine (i.e., for decreasing engine speed
while the vehicle is in a braked stationary state, and for
increasing vehicle engine speed again subsequent to termination of
the braked state) is mounted on the vehicle. The ECU 10 is
primarily made up of a microprocessor, and is provided with an
input circuit and an output circuit.
An engine-speed sensor 11, vehicle-speed sensor 12, idle switch 12,
and shift-position switch 14 are connected to the ECU 10. The ECU
10 can detect engine speed, vehicle speed, whether the accelerator
pedal has been released, and the position of the shift lever of the
automatic transmission 5 according to signals from the sensors.
Further, a brake pedal operated-quantity sensor 15 is connected to
the ECU 10. As shown in FIG. 2, this brake pedal operated-quantity
sensor 15 converts a brake pedal operated quantity to an electrical
signal. In FIG. 2, position A represents the pedal position when
there is no pedal depression, and position D represents the maximum
depression position of the brake pedal 20.
In FIG. 1, a road surface slope sensor 16 is connected to the ECU
10. This road surface slope sensor 16 detects the angle of slope of
the road surface. As shown in FIG. 3, a sensor may be utilized in
which a movable contact point 22 is connected with a depending
weight 21. The movable contact point 22 is slidable on a circular
resistor 23, a predetermined voltage is applied at the two ends of
the resistor 23, and the potential at the area of contact with the
movable contact point 22 is measured and output.
As shown in FIG. 1, the ECU 10 can send a fuel-cutoff signal and an
ignition-cutoff signal to the ECU 4 that stops the engine 1.
Additionally, the ECU 10 can send a fuel-injection signal and an
ignition signal to the ECU 4, to perform fuel-injection operation
and ignition operation of the engine 1. Further, a starter (motor)
17 is connected to the ECU 10, and the ECU 10 performs drive
control for the starter 17.
A mode of operation of an engine automatic speed control apparatus
for a vehicle of such structure will be described next.
FIGS. 4 and 5 are processing flow diagrams for automatic engine
stopping and starting, while FIG. 6 is a timing diagram. FIG. 6
shows the state of the brake pedal operated quantity, the engine
speed, the vehicle speed, the engine-cutoff signals (fuel-cutoff
signal and ignition-cutoff signal), the engine "on" signals
(engine-ignition signal and fuel-injection signal), the starter,
and the idle switch. In FIG. 6, depression of the brake pedal 20
starts at time t1 and continues until maximum depression at t3,
which stops the vehicle. Thereafter, brake depression begins to be
relaxed at time t4, and startoff is enabled when the vehicle
operator releases his or her foot from the brake pedal 20 at t7. At
time t8, depression of the accelerator pedal starts, causing the
vehicle to travel.
The ECU 10 determines whether an engine-stopping condition has been
fulfilled at steps 101-106 of FIG. 4. Specifically, at step 101,
the ECU 10 determines whether engine speed is at or below idle
speed, and at step 102 the ECU 10 determines whether vehicle speed
is "0." At step 103, the ECU 10 determines whether the idle switch
has been switched on without operation of the accelerator
pedal.
At step 104, the ECU 10 determines whether braking force due to
operation of the brake pedal 20 is greater than braking force to
inhibit vehicle movement in correspondence with road surface slope
angle. More specifically, the ECU 10 calculates required braking
force (i.e., amount of pedal depression) F corresponding to the
road surface slope angle according to the road surface slope sensor
16 using a map shown in FIG. 7, adds a predetermined margin
quantity to this calculated value, and determines whether
depression of the brake pedal greater than this amount of
depression has been performed. Characteristic curve L1 of the map
shown in FIG. 7 depicts previously determined braking force to
inhibit vehicle movement corresponding to the road surface slope
angle. In other words, when the brake pedal 20 is depressed from
position A in FIG. 2, position B which can prevent rolling of the
vehicle is reached, and rolling of the vehicle can reliably be
prevented when the amount of pedal depression exceeds position
C.
In this way, when the brake pedal 20 is further depressed to exceed
position C (i.e., when the brake pedal is in region Z3 in FIG. 2),
the determination at step 104 of FIG. 4 is "YES." Stated another
way, the depression position (position B in FIG. 2), which can
prevent rolling of the vehicle, changes in correspondence with the
slope angle of the road surface. However, the ECU 10 calculates the
amount of depression to prevent rolling of the vehicle from the
slope of the road surface detected by the road surface slope sensor
16.
At step 105 in FIG. 4, the ECU 10 determines whether the shift
lever is at "Drive" (D), "2nd Speed," or "1st Speed." At step 106,
the ECU 10 determines whether other prohibiting conditions (engine
coolant-water temperature being in a predetermined temperature
range, no abnormality in charging system and battery state being
favorable) are fulfilled.
Accordingly, when these conditions are obtained and the
engine-stopping condition is fulfilled (time t2 in FIG. 6), the ECU
10 transfers execution to step 107 in FIG. 4 and sends the
fuel-cutoff signal and the ignition-cutoff signal to the ECU for
engine-controlling use 4, causing the engine to stop
automatically.
Accordingly, after the processing for stopping the engine 1 is
completed, the ECU 10 transfers to the engine starting processing
in FIG. 5.
In FIG. 5, the ECU 10 determines whether an engine starting
condition has been fulfilled at steps 201-203. Specifically, at
step 201 the ECU 10 determines whether engine speed is less than a
predetermined value, and the engine is stalled. At step 202, the
ECU 10 determines whether the shift lever is at "Drive" (D), "2nd
Speed," or "1st Speed." At step 203, the ECU 10 determines whether
the brake pedal 20 has been relaxed and braking force is less than
or equal to braking force to inhibit vehicle movement in
correspondence with the road surface slope angle. More
specifically, the ECU 10 calculates the required braking force
(i.e., amount of pedal depression) F corresponding to the road
surface slope angle from the road surface slope angle according to
the road surface slope sensor 16 using the map shown in FIG. 7,
adds a predetermined margin quantity to this calculated value, and
determines whether depression of the brake pedal less than or equal
to this amount of depression has been performed. That is to say,
the ECU 10 determines whether depression of the brake pedal 20 has
been relaxed beyond position C in FIG. 2 employed in determination
of engine stoppage and has entered pedal-operation region Z2.
Accordingly, when these conditions all obtain and the starting
condition for the engine 1 is fulfilled (time t5 in FIG. 6), the
ECU 10 transfers execution to step 204 in FIG. 5 and sends the "on"
signals (the engine 1 ignition signal and fuel-injection signal) to
the ECU for engine-controlling use 4 to restart the engine, causing
fuel injection and ignition to start. Additionally, in step 205 the
ECU 10 actuates the starter 17 and starts the engine 1.
Thereafter, when engine speed ne exceeds engine combustion speed
ne0 at step 206 (time t6 in FIG. 6), the engine is considered to
have experienced complete combustion, and at step 207 the ECU 10
halts actuation of the starter 17, thereby stopping the starter
17.
As a result, after engine stoppage, the engine 1 is restarted in
the interval during which the brake pedal 20 is in the region Z2 in
FIG. 2, that is, in the interval after alleviation of braking force
due to the brake pedal 20 until the brake pedal 20 is released.
Therefore, a smooth startoff with minimal time lag associated with
engine starting becomes possible. Additionally, inching utilizing
the creeping force associated with an automatic-transmission
vehicle becomes possible. Further, when starting off on a grade,
startoff can be accomplished with no associated slip-back.
More particularly, when engine automatic-stopping conditions such
as vehicle speed at "0," accelerator off, favorable battery state,
and so on are fulfilled and the vehicle braking force is at or
above a predetermined value, that is to say, when the engine is
automatically stopped when sufficient braking force that prevents
vehicle rolling can be ensured and the braking force is less than
or equal to a predetermined value in an engine-stopped state, the
engine is automatically restarted when braking force is weak while
sufficient braking force to prevent vehicle rolling is ensured.
Consequently, startoff can be accomplished with no slip-back not
only on a level road, but on a grade as well.
Therefore, in the present embodiment, the ECU 10 restarts the
engine 1 in an interval after alleviation of braking force via the
brake pedal 20 until the brake pedal 20 is released, and so the
engine is started quickly, and sufficient engine output is obtained
when the accelerator is actuated after releasing the brake. In
particular, in a vehicle provided with an automatic transmission
with a torque converter 5, travel via creeping can be performed,
wherein the vehicle moves slowly when the shift lever is in a
position for travel even when the accelerator pedal 20 is not
depressed.
Also in this embodiment, because sufficient braking force such that
the vehicle does not move is determined in correspondence with the
slope of the road surface utilizing the road surface slope sensor
16 as the road surface slope-detecting unit, the larger the slope,
the greater the necessary setting for the braking force, and so
slip-back of the vehicle can reliably be prevented.
In addition, in the present embodiment, the brake pedal
operated-quantity sensor 15 is utilized as the operated-quantity
detecting unit, and so a braking state can be detected via a simple
structure.
As a sample application of the present embodiment, a linear brake
pedal operated-quantity sensor 15 may be utilized to continuously
measure the position (operated quantity) of the brake pedal 20.
However, as shown by signal waveform SG1 in FIG. 8, a switch which
is switched on or off at a predetermined depressed position of the
brake pedal 20 may alternatively be used. By providing a switch
which outputs a switching signal at a predetermined depressed
position of the brake pedal 20 and adopting a structure to detect
braking force therewith, overall system structure is simplified and
cost is reduced.
Additionally, brake pressure may be measured directly instead of
detecting the operated quantity of the brake pedal 20. That is, a
hydraulic-pressure sensor to detect brake pressure may be utilized
in substitution for the brake pedal operated-quantity sensor 15. In
this way, the braking state can accurately be detected by detecting
brake pressure and taking this detected brake pressure to be the
vehicle braking force.
It is also acceptable to utilize a linear brake pedal
operated-quantity sensor 15 to continuously measure the position of
the brake pedal 20, and as shown in FIG. 9, determine whether the
operated speed of the brake pedal 20 is positive or negative in
order to detect the direction of pedal operation, and, when the
operated speed of the brake pedal 20 is negative (time t4 in FIG.
9), restart the engine. As a result, the braking state can be
detected via a simple structure, and the intent of the driver can
be accurately detected by detecting the operated speed of the brake
pedal 20.
Additionally, although a structure utilizing a foot brake braking
force has been described, a structure utilizing braking force of,
for example, a parking brake may alternatively be utilized.
Second Embodiment
A second embodiment will be described hereinafter, primarily with
respect to how it differs from the first embodiment.
As shown in FIG. 10, a brake pedal 20 interlocks with a master
cylinder 30. The master cylinder 30 and a wheel cylinder 31 are
interconnected with a hydraulic conduit 29, hydraulic pressure
generated by the master cylinder 30 is transmitted to the wheel
cylinder 31, and the vehicle wheel is braked. Herein, with this
embodiment, a solenoid 32 is disposed in the hydraulic conduit 29
(i.e., in the hydraulic circuit) between the brake pedal 20 and the
master cylinder 30. This solenoid 32 is a normally-open valve and
closes the hydraulic circuit when actuated by a coil 32a,
maintaining the brake hydraulic pressure at the wheel cylinder 31.
Accordingly, brake pressure is maintained even when the brake pedal
20 is released by actuating (exciting) the coil 32a of the solenoid
32 when the brake pedal 20 is depressed. This control of the
solenoid 32 is executed by the ECU 10 as shown in FIG. 1.
A mode of operation of an engine automatic speed control apparatus
for a vehicle of such structure will be described next. After
stopping of the engine via processing similar to that shown in FIG.
4, processing for starting the engine is started. FIG. 11 is a flow
diagram for engine automatic restarting, and FIG. 12 is an
associated timing diagram.
After an engine starting condition is fulfilled at steps 301-303 of
FIG. 11, at step 304 the ECU 10 drives the solenoid 32 to maintain
the braked state (time t10 in FIG. 12). That is to say, the brake
pedal 20 is in a depressed state that prevents rolling of the
vehicle, and so the stopped state of the vehicle can be maintained
via the brake pressure.
Accordingly, at step 305 the ECU 10 begins engine fuel injection
and ignition, and at step 306 the ECU 10 actuates the starter 17
and starts the engine. At step 307, when the engine speed ne
exceeds the combustion speed ne0 (for example 300 rpm; time t11 in
FIG. 12), the ECU 10 determines that complete combustion has
occurred in the engine, and at step 308 the ECU 10 halts actuation
of the starter 17. Accordingly, at
step 309, when the engine speed ne exceeds speed ne1 (for example
400 rpm) sufficient to drive the vehicle (time t12 in FIG. 12), the
ECU 10 transfers execution to step 310 and releases the brake
pressure held at step 304.
When the output of the starter 17 is large and the crank speed
during engine starting is high, that is to say, when ne1 is
believed to be less than ne0, the sequence of determination of the
"off" state of the engine starter 17 (steps 307 and 308 in FIG. 11)
and determination of release of held brake pressure (steps 309 and
310 in FIG. 11) is reversed.
With the above-described structure, vehicle startoff on a grade
with no slip-back becomes possible irrespective of driver
operation.
That is to say, when the driver misjudges the amount of slope when
starting off on a grade and the braking force applied by the driver
is weak with respect to the amount of slope during engine starting,
vehicle slip-back is possible. However, vehicle slip-back can
reliably be prevented by providing the solenoid 32 to control
vehicle braking irrespectively of driver operation, holding the
braking force and automatically restarting the engine when braking
force due to driver operation in an engine-stopped state is a
predetermined value or less, and releasing the vehicle braking
after generation of sufficient drive force (creeping force) to
cause the vehicle to advance after engine starting.
As described above, the ECU 10 and the solenoid 32 are utilized as
the braking force controlling unit. However, a device which itself
generates braking force may also be utilized. The solenoid was
utilized in the above-described example to ensure vehicle braking
force by the driver at the start of brake operation. In this case,
the brake pressure is maintained and vehicle braking can be ensured
by closing the solenoid 32 disposed in the hydraulic brake circuit.
Along with this, brake pressure to brake the vehicle can be
released, and braking force can be controlled via a simple
structure without adding a new source of motive power by opening
the solenoid 32 after restarting the engine.
As a result, in the present embodiment, a braking force controlling
unit (the ECU 10 and the solenoid 32) is provided to apply
predetermined braking force such that the vehicle does not move
while the engine is stopped, and so startoff with no slipping of
the vehicle becomes possible irrespectively of driver brake
operation.
The solenoid 32 disposed in the hydraulic circuit from the master
cylinder 30 to the wheel cylinder 30 is preferred from a practical
standpoint, because the predetermined braking force is released
when engine speed is greater than or equal to a predetermined
value.
Third Embodiment
A third embodiment will be described hereinafter, primarily with
respect to differences between it and the second embodiment.
After processing stops the engine as in FIG. 4, execution is
transferred to processing for starting the engine. FIG. 13 is a
flow diagram for engine automatic restarting, and FIG. 14 is an
associated timing diagram. This embodiment interposes step 410 of
FIG. 13 between steps 309 and 310 of FIG. 11, adding one more
condition for brake-pressure release.
To go into greater detail, when an engine starting condition is
fulfilled at steps 401-403 (time t10 in FIG. 14), at step 404 the
ECU 10 maintains the brake pressure. At step 405 the ECU 10 begins
engine fuel injection and ignition, and at step 406 the ECU 10
actuates the starter 17 and starts the engine. At step 407, when
the engine speed ne exceeds the combustion speed ne0 (time t11 in
FIG. 14), the ECU 10 determines that complete combustion has
occurred and at step 408 the ECU 10 halts actuation of the starter
17 and stops the starter 17.
Accordingly, when the engine speed ne exceeds speed ne1 sufficient
to drive the vehicle (time t12 in FIG. 14) at step 409 and the ECU
10 detects depression of the accelerator pedal at step 410 (time
t20 in FIG. 14), the ECU 10 transfers execution to step 411 and
releases the brake pressure held at step 404.
Consequently, during the period from stopping to starting the
engine, not only is there no vehicle slip-back, but the vehicle
also does not begin to move with just the release of the brake,
irrespectively of operation by the driver.
With the above-described structure, during vehicle startoff on a
grade, not only does vehicle startoff with no slip-back become
possible irrespectively of operation by the driver, but also
braking is not released unless starting of the engine and
depression of the accelerator are detected. Therefore, not only
does the vehicle not begin to move with starting of the engine, but
the intent of the driver to start off can be accurately reflected,
thereby enhancing safety.
As a result, in the present embodiment, braking is released when a
rise in engine speed and accelerator depression are detected.
Therefore, the vehicle does not begin to move even when the brake
is released and the engine is started, and the intent of the driver
to start off as indicated by depressing the accelerator can be
accurately reflected.
Fourth Embodiment
A fourth embodiment will be described hereinafter, chiefly with
respect to differences between it and the third embodiment.
After stopping of the engine by processing for automatic engine
stopping similar to FIG. 4, execution is transferred to processing
for starting the engine. FIG. 15 is a flow diagram for engine
automatic restarting. With this embodiment, when the slope angle of
the road surface is less than or equal to a predetermined value at
step 501 of FIG. 15, the processing at step 404 to hold the brake
pressure is bypassed, and the processing to hold the brake pressure
is executed solely when the slope angle of the road surface is
greater than or equal to a predetermined value.
That is to say, whereas with the second and third embodiments the
braking force of the vehicle is maintained during automatic engine
stoppage with no distinction between whether the stopped state of
the vehicle is on a level road surface or on a grade, with the
present embodiment the slope state of the road surface is detected,
and braking of the vehicle is controlled solely when the slope
angle of the road surface is greater than or equal to a
predetermined value, thus avoiding consumption of electrical power
to actuate the coil of the solenoid 32 when the vehicle is stopped
on a level road. That is, application of braking force is
prohibited, and electrical power consumption is suppressed, when
the slope angle of the road surface is greater than or equal to a
predetermined value.
Fifth Embodiment
A fifth embodiment will be described hereinafter, primarily with
respect to differences between it and the third embodiment. After
the vehicle is stopped in a manner similar to that shown in FIG. 4,
execution is transferred to processing for starting the engine.
FIG. 16 is a flow diagram for engine automatic restarting, and FIG.
17 is an associated timing diagram.
When an engine starting condition is fulfilled at steps 401-403 of
FIG. 16, at step 403 the ECU 10 holds the brake pressure and at
steps 405-408 the ECU 10 initiates engine cranking. Thereafter, at
step 601, when the engine speed is uniform at a predetermined
timing and engine speed is equal to idle speed (time t30 in FIG.
17), at step 411 the ECU 10 releases a predetermined braking
force.
That is to say, the brake is released when idle speed is reached
after initial spiked engine speed during engine starting, and so
lurching due to the initially spiked engine speed immediately after
starting can be prevented.
Sixth Embodiment
A sixth embodiment will be described hereinafter, primarily with
respect to differences between it and the second embodiment.
FIG. 18 is a timing diagram for this embodiment, which is
structured with the operated state of a parking brake also being
taken into account.
To go into more detail, when the driver operates the parking brake
and releases the foot brake (brake pedal) to maintain the vehicle
in a stopped state while the engine is stopped, the time for which
the brake is held until vehicle startoff becomes lengthy, and coil
heating becomes a concern.
As a result, this embodiment employs a structure which will be
described hereinafter.
As shown in FIG. 1, a parking-brake operated-quantity sensor 40 is
connected to the ECU 10. This parking-brake operated-quantity
sensor 40 detects the operated quantity of the parking brake.
Accordingly, the operated state of the parking brake is monitored
when an engine-restarting condition is fulfilled at time t40 in the
timing diagram of FIG. 18, and when the parking brake is in an
operated state, holding of braking force is not performed.
That is to say, when the parking brake is operated and the brake
pedal 20 is released to maintain the vehicle in a stopped state
while the engine is stopped as shown in FIG. 12, holding of the
braking force is performed immediately when braking force due to
the brake pedal 20 drops below a predetermined value at time t40
while the pressure on the brake pedal 20 is being relaxed, as shown
in FIG. 19. In contrast thereto, with the embodiment depicted in
FIG. 18, when the parking brake is pulled at the same time t40,
heat generation accompanying prolonged actuation of the coil of the
solenoid 32 can be prevented without outputting a braking force
holding signal.
Therefore, when the braking force of another unit (i.e., the
parking brake) becomes greater than or equal to a predetermined
value when braking force due to the brake pedal 20 becomes less
than or equal to a predetermined value, application of braking
force is prohibited, and so heat generation by the coil of the
solenoid 32 can be suppressed.
Seventh Embodiment
A seventh embodiment will be described hereinafter, primarily with
respect to differences between it and the sixth embodiment.
FIG. 20 is a timing diagram for this embodiment. This embodiment
modifies the sixth embodiment so as to avoid shortening of the time
the engine is stopped.
To go into greater detail, with the sixth embodiment, as shown in
FIG. 12, the engine is restarted when the braking force due to the
brake pedal 20 falls below a predetermined value at time t50 while
the pressure on the brake pedal 20 is being relaxed. In contrast
thereto, a structure which will be described hereinafter is
employed to avoid shortening of the time the engine is stopped.
A coil-temperature sensor 50 (refer to FIG. 1) is utilized to
monitor the temperature of the coil 32a of the solenoid 32.
Accordingly, when the parking brake has not been pulled at the time
t50 in FIG. 20 while the pressure on the brake pedal 20 is being
relaxed, the solenoid 32 is driven. Thereafter, when the coil
temperature reaches a predetermined temperature T1 due to actuation
of the coil 32a (time t51 in FIG. 19), starting of the engine
begins. Accordingly, after the starter is switched off at time t52,
when engine speed has reached the speed ne1 sufficient to drive the
vehicle at t53, the solenoid 32 is switched off and the braking
force is released. As a result, the stopped state of the engine is
continued for the interval from t50 to t51 in FIG. 20 (i.e., the
time indicated by .increment.t), and the coil temperature of the
solenoid 32 also does not rise above an upper-limit value T0 of
usage temperature. Stated another way, a comparative value T1 is
set so as not to rise above the upper-limit value T0 of usage
temperature.
Therefore, in this embodiment, when the coil temperature of the
solenoid 32 reaches a predetermined temperature, the ECU 10
restarts the engine, and so engine-stopped time can be lengthened
while taking heat generation of the coil into account.
As a sample application of this embodiment, instead of monitoring
the temperature of the coil of the solenoid 32, it is also
acceptable to initiate a timer-count operation at the start of
operation of the solenoid 32, and when an operation time C0
extending from t60 to t61 is reached, begin starting of the engine,
as shown in FIG. 22. When restarting of the engine is triggered
after a predetermined time has elapsed after initiating operation
of the solenoid 32 in this way, the temperature sensor 50 is not
required. Therefore, system cost can be reduced.
Eighth Embodiment
An eighth embodiment will be described hereinafter, primarily with
respect to differences between it and the second embodiment.
FIG. 23 is a timing diagram for this embodiment. This embodiment
also is structured also to take the operated state of the parking
brake into account. This embodiment provides a mechanism to
maintain the braking force of both the foot brake and the parking
brake. Namely, a braking force holding device for parking-brake use
60 is provided in addition to the solenoid for foot-brake use 32,
as shown in FIG. 1. A system which chucks the wire of the parking
brake or the like can be utilized as the braking force holding
device for parking-brake use 60.
Accordingly, operation of the foot brake is begun at time t70 in
FIG. 23, maximum depression amount is reached at t72, operation of
the parking brake is begun at t73, a maximum amount is reached at
t74, and thereafter the foot brake is released, and the parking
brake is released at startoff.
In this case, an operation to hold the braking force is executed
when the sum of braking force due to the foot brake and braking
force due to the parking brake is equal to or less than a
predetermined value. That is to say, in a case where the vehicle is
stopped utilizing the foot brake for stopping the vehicle and
thereafter the parking brake is pulled, as shown in FIG. 23, brake
holding begins at time t76 whereat the parking brake is relaxed to
a certain extent.
In this way, after the starting condition for the engine is
fulfilled and holding of brake pressure and engine starting have
begun, when the engine speed ne exceeds the combustion speed ne0
(time t77 in FIG. 23), the starter 17 is stopped. When the engine
speed ne has reached the speed ne1 sufficient to drive the vehicle
(time t78 in FIG. 23), the held brake pressure is released.
Accordingly, as is illustrated at the very bottom of FIG. 23,
braking force due to the foot brake falls below a predetermined
value at time t75. In a case where this is taken to be the trigger
for holding braking force, the holding operation is performed for a
prolonged period. However, this phenomenon can be avoided with the
present embodiment.
As a result, in this embodiment, the ECU 10 starts to apply braking
force when the sum of the respective braking forces of the
plurality of braking force operating members (i.e., the foot brake
and the parking brake) is less than or equal to a predetermined
value, and so wasteful braking force holding operation can be
avoided. This embodiment is preferred particularly from the
standpoint of suppressing heat generation by the coil of the
solenoid 32.
Cases of application in a vehicle provided with an automatic
transmission were described hereinabove, but application in a
vehicle provided with a manual transmission is also
contemplated.
While the above description constitutes the preferred embodiment of
the present invention, it should be appreciated that the invention
may be modified without departing from the proper scope or fair
meaning of the accompanying claims. Various other advantages of the
present invention will become apparent to those skilled in the art
after having the benefit of studying the foregoing text and
drawings taken in conjunction with the following claims.
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